Gas Laws Practice Communication Problems
1. What factors would change the molar volume of a gas and how
would they change it?
2. If you have ever gone camping, you may have used a propane
powered gas stove. The gas canister is filled with compressed
gaseous fuel which is slowly vented to the stove above for
combustion. As the gas canister empties, you may have noticed
that it becomes cold to the touch. Use any relevant gas laws to
explain this phenomenon.
3. IN WORDS, state TWO of the proportionalities found by Boyle,
Charles or Gay-Lussac. To correctly identify each scientist’s
contribution is ideal (no pun intended), but not required.
Provide a simple example of where each of these
proportionalities can be viewed in nature. Be sure to state under
what conditions each proportionality holds true.
4. What is the difference between a closed and an open system?
How would this have an effect on gas laws?
1. What factors would change the molar volume of a gas and how
would they change it?
Notes:
- Define molar volume
- Increase pressure = decreased volume
- Increased temperature = increased volume
Answer:
The volume of one mole of gas can be changed by two main
factors. If the pressure is increased, then one mole of a gas will be
compressed into a smaller volume. If the temperature of one mole
of gas is increased, then the spaces between its particles will
increase and it will take up a greater volume.
2. If you have ever gone camping, you may have used a propane
powered gas stove. The solid metal gas canister is filled with
compressed gaseous fuel which is slowly vented to the stove
above for combustion. As the gas canister empties, you may
have noticed that it becomes cold to the touch. Use any
relevant gas laws to explain this phenomenon.
Notes:
- Metal canister volume does not change
- Pressure lowers as gas escapes
- Temperature lowers as gas escapes
- Gay-Lussac’s law = direct proportionality between pressure and
temperature
Answer:
The propane gas canister cools as it empties according to GayLussac’s gas law. The Gay-Lussac gas law states that pressure is
directly proportional to temperature when the volume is kept
constant. As the gas is released the pressure in the canister must
decrease. Since the volume of the gas canister does not change,
then we must assume that the temperature will decrease
proportionately as the pressure decreases.
3. IN WORDS, state TWO of the proportionalities found by Boyle,
Charles or Gay-Lussac. To correctly identify each scientist’s
contribution is ideal (no pun intended), but not required.
Provide a simple an example of where each of these
proportionalities can be viewed in nature. Be sure to state under
what conditions each proportionality holds true.
Notes:
- Boyle = Volume is inversely proportional to pressure when temperature is constant
Eg. Air can be kept compressed in a small SCUBA tank
- Charles = Volume is directly proportional to temperature when pressure is constant
Eg. a sealed milk carton expands when left on counter after refrigeration
-
Gay-Lussac = Pressure is directly proportional to temperature when the volume is
constant
Eg. CO2 canister becomes freezing cold when the pressure is released.
Answer:
Gas laws describe how “ideal” gases behave when only one factor is
changed. Boyle’s law states that for ideal gases volume is inversely
proportional to pressure when the temperature is kept constant. This
means that as volume increases, the pressure will decrease
proportionately and vice versa. We see this in nature in the human
lungs. When the diaphragm lower and rib cage expands, the
increased lung volume creates a low pressure which draws more air
in. Charles’ law states that volume is directly proportional to
temperature when the pressure is kept constant. This means that low
temperatures result in low pressures and vice versa. We see this in
car tires. In the winter when the temperature lowers, the tire
pressure decreases and we need to add more air.
4. What is the difference between a closed and an open system?
How would this have an effect on gas laws?
Notes:
- Open = gas can enter or leave the system
- Closed = fixed mass of gas
- Gas laws only apply to closed systems
Answer:
In order for ideal gas laws to be followed, they must be within a
closed system. This means that the amount of gas is fixed. No new
gas and enter or leave the system. For example, Boyle’s law could
not be observed in an open system. If the system were open,
changing the volume would increase the pressure, however, this
would force gas out of the system until the pressure lowered again
to equalize with the surroundings.